Defining models of glacial isostatic adjustment in West Antarctica and Antarctic Peninsula (UKANET): better constraints on Earth structure and uplift

Lead Research Organisation: University of Leeds
Department Name: School of Earth and Environment

Abstract

We aim to decrease the uncertainty associated with the measurement of ice mass change in West Antarctica by addressing our lack of knowledge of Earth structure and accuracy of present-day uplift rates. Ice loss from the West Antarctic Ice Sheet (WAIS) currently accounts for around 10% of present-day global sea-level rise. Moreover, this region is undergoing accelerated ice loss. Accurate projections for the evolution of WAIS are currently hindered by uncertainties in measurements of present-day ice mass change. Two key methods for deriving this change are satellite gravimetry, which determines changes in Earth's gravity field due to surface mass redistribution, and altimetry, which measures modifications to the height of the ice surface. Crucially, both of these techniques are susceptible to errors introduced by correcting for the uplift response of the solid Earth to past ice mass loss, a process known as Glacial Isostatic Adjustment (GIA). GIA models require information relating to the regional deglaciation history and the rheological properties of the solid Earth. In most GIA models only 1D global averages of Earth structure are taken in to account; this is a gross oversimplification.
We propose to determine (i) 3D Earth structure in West Antarctica and Antarctic Peninsula through a new passive seismological experiment and (ii) present-day uplift rates through the extension of a NERC-funded GPS network in the Peninsula and new spatially extensive satellite radar interferometry data (InSAR). We will deploy 10 broadband seismometers for 2 years, adjacent to a contemporaneous 2 year POLENET deployment, to estimate 3D variations in Earth rheology by determining S-wave velocity-depth models down to depths of 400 km. Seismic data have never been collected in the southern Antarctic Peninsula region of West Antarctica, and hence very little is known about its Earth structure. The determination of lithospheric structure will also improve our understanding of the tectonic evolution of the region. We propose a 3 year PDRA to carry out the fieldwork and seismological research.
Long time series of surface deformation measurements are important to our understanding of uplift rates due to GIA. A network of 10 GPS sites has been deployed in the southern Antarctic Peninsula since 2009 under a now terminating NERC/AFI grant. At minor additional financial cost, but with significant scientific benefit, we propose to operate this network for a further 2 years. Our Project Partner Matt King (University of Tasmania) will oversee the processing of these data. The seismic structure results will be incorporated into a 3D GIA model as an addition to CI Whitehouse's Fellowship work; a 1.5 year PDRA will combine the GIA and deformation results to more tightly constrain past and present ice mass change in the southern Antarctic Peninsula and West Antarctica.
While the sparse network of GPS will constrain the deformation pattern on a broad scale, we expect smaller wavelength variability in deformation due to present-day ice mass change. Therefore, we plan to apply satellite radar interferometry (InSAR) to the rock outcrops in West Antarctica to increase the spatial sampling of the deformation field by orders of magnitude. Because distances between rock outcrops can be large, the spatial variability of the tropospheric radar propagation delay during interferometric processing has to be estimated from weather models. We propose to test these assumptions with a local field deployment of 6 GPS in the Antarctic Peninsula.
The timing of this grant proposal is critical as 1) BAS logistics are already in place for the funded 2 year iStar programme in the south of the region; 2) US POLENET seismometers will temporarily be positioned to the south and significantly extend our station coverage; 3) the grant supporting the GPS network is ending.

Planned Impact

Who will benefit from our research?
The main beneficiaries of knowledge arising from this project are policy makers, such as the Intergovernmental Panel on Climate Change (IPCC) and the UK Environment Agency (EA), charged with policy and planning related to robust projections of future sea level rise. The Living With Environmental Change (LWEC) initiative, established by the UK government, could use the outputs from this research to improve the capacity of government, business and society to mitigate and adapt to environmental change.

We aim to benefit the general public by furthering their understanding of uncertainty in science using GIA models, ice mass balance and sea level rise as our proxies. We hope to extend this theme out to industry and policy makers in government. We will demonstrate how scientific research can be used to address and reduce uncertainty, but also explain why uncertainty is inherent in the science of sea level rise.

How will they benefit from the research?
This research will help to reduce the uncertainty associated with projections of future sea level rise and the subsequent risk associated with sea-defence planning and coastal adaptation. Our results will evidence and support UK's own sea-level projections, which EA have been developing in conjunction with the Hadley Centre and British Antarctic Survey (BAS) as a response to limitations in the global projections of the IPCC. The IPCC AR5 is currently in draft, and will be published in 2013/14. It will include specific sea-level rise projections to 2100 that will be based almost exclusively on the evidence provided in the peer-reviewed literature. The papers coming out our project will hopefully influence subsequent IPCC drafts.

Publications

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Lucas E (2022) Shear Wave Splitting Across Antarctica: Implications for Upper Mantle Seismic Anisotropy in Journal of Geophysical Research: Solid Earth

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Lucas E (2021) Seismicity and Pn Velocity Structure of Central West Antarctica in Geochemistry, Geophysics, Geosystems

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Selway K (2019) Upper Mantle Melt Distribution From Petrologically Constrained Magnetotellurics in Geochemistry, Geophysics, Geosystems

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Selway K (2019) A small, unextractable melt fraction as the cause for the low velocity zone in Earth and Planetary Science Letters

 
Description The UKANET seismic recordings from the 10 sensors distributed across West Antarctica have been analysed by Leeds and Durham universities in the UK, and collaborators in the USA, to determine the lateral variability in Earth structure down to about 250 km across West Antarctica. This new information has been fed in to computer models predicting Earth deformation, and by implication sea-level, caused by global warming and the on-going ice melt across West Antarctica.
Exploitation Route All the collected data have been archived such that they are readily available by the world-wide community of seismologists
Sectors Environment

 
Description Tested and deployed the first UK network of seismic broadband equipment in West Antarctica. As of February 2018 two years of data and the equipment successfully brought back. The analysis of the data collected has resulted in a 3D earth structure model of West Antarctica that has bee used by collaborators to predict sea level rise due to long term ice-melt in the region.
First Year Of Impact 2018
Sector Environment
Impact Types Societal,Economic

 
Title Deployment of GPS equipment in Antarctica 
Description UKANET GNSS Installation 2014 / 2015 Professor A. Hooper (Leeds University) with BAS support deployed 6 Leeds Leica GS10 continously receording GPS + GLONASS observations, with 15 s sample interval in the Antarctic Peninsula during the austral fieldwork season 2014 / 2015. The details of the deployment are as follows: Station Lat (S) Long (W) Elevation Start End deg min sec deg min sec m UKA5 65 53 43.81 63 02 09.25 859 19/11/14 1/15 UKA6 66 01 49.91 62 52 43.72 807 19/11/14 1/15 UKA4 65 48 34.21 62 38 24.89 770 26/11/14 12/15 UKA2 65 34 33.57 62 34 49.64 691 26/11/14 1/15 UKA3 65 45 10.32 62 29 55.12 395 3/12/14 12/15 UKA1 65 30 59.02 62 33 33.07 799 3/12/14 1/15 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact This data are in the process of being worked upon 
 
Title Deployment of seismological equipment in Antarctica 
Description UKANET Seismological station installation 2015 / 2016 Dr JP O'Donnell (Leeds University) and Dr A Brisbourne (BAS) with BAS support deployed 10 broadband seismological stations in West Antarctica during the austral season 2015 / 2016. The equipment deployed was purposively compatible with that of the successful PASSCAL Polenet deployments (www.polenet.org) and will be deployed for 2 years. State-of-Health messages are being sent every 24 hours via Iridium satellite to check the data streams. The first year's data will be collected during the 2016 / 2017 Antarctic season. Seismological equipment tested and purchased 10 Guralp CMG 3P broadband (120s) sensors (NERC Geophysical Equipment Pool) 10 Quanterra 330 digitisers including GPS 10 Xeos Iridium state-of-health satellite communication systems 10 PASSCAL polar sensor and recording thermal housing 10 Solar Power units including Lithium battery packs. The details of the deployment are as follows: Station Lat (S) Long (W) Elevation Start Date deg deg m UKA01 ROTH ROTH 67.51991 068.14884 264.0 2016,011-2017,014 UKA02 FOSS FOSS 71.31459 068.30542 83.6 2016,103-2017,010 UKA03 KIBB KIBB 75.27601 065.60490 1173.2 2016,016-2017,008 UKA04 ZK15 FOWL 76.89274 079.30112 1344.2 2016,044-2016.341 UKA05 ZF15 PIG2 74.45562 097.68298 984.6 2016,029-2016,361 UKA06 ZE15 PIG1 73.97817 097.57499 1045.4 2016,028-2016,363 UKA07 ZG15 PIG3 75.08396 097.47446 653.6 2016,030-2016,359 UKA08 PIGD PIGD 75.80252 100.27584 840.5 2016,031-2018,352 UKA09 ZJ15 KEAL 76.52028 085.69965 1036.8 2016,045-2017,006 UKA10 ZH15 PIG4 75.75985 097.58304 762.0 2016,030-2016,356 The deployment was delayed by poor visibility and flying conditions for 2 weeks whilst in Antarctica (see start dates above for UKA04 and 09). Instruments were serviced and maintained by Dr JP O'Donnell and Charles Dunham (part-time phd student) from 1st December 2016 to 24th January 2017, with the help of British Antarctic Survey. About 11 months of seismological data were collected for further analysis. Of the 10 stations deployed, 2 were found to have faulty NERC seismometers. Due to snow accumulation (up to 2.2m, completely over the solar panels) a significant amount of digging was required to maintain some of the sensors. To optimise data coverage some of the equipment was moved as follows: UKA01 WELC WELC 70.7318 063.8274 1561.9 2017,018- UKA03 KIBB KIBB 75.2759 065.6049 1168.3 2017,008- UKA04 ZK15 FOWL 76.8927 079.3011 1337.9 2016,341- UKA05 ATOL ATOL 71.3896 068.8703 732.8 2017,010- UKA06 ZE15 PIG1 73.9781 097.5751 1057.1 2016,363- UKA07 ZG15 PIG3 75.0839 097.4746 648.8 2016,359- UKA08 PIGD PIGD 75.8024 100.2758 843.6 2016,349- UKA09 ZJ16 ZJ16 75.5193 085.7077 1187.6 2017,006- UKA10 BREN BREN 72.6749 063.0208 1678.9 2017,019- During this maintenance BAS and Leeds personnel gained significant experience in the deployment of broadband sensors under Antarctic conditions. This is the first time NERC has deployed such instruments in such an environment at such a scale. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact As well as the American Polenet seismological data, we can now analyse our own bespoke seismological data set to study the crust and upper mantle structure 
URL http://ukanet.wixsite.com/ukanet
 
Title 3D shear wave (Vsv) velocity model of West Antarctic crustal structure 
Description 3D vertically-polarised shear wave (Vsv) velocity model of West Antarctic crustal structure developed using data from the 2016-2018 UK Antarctic Seismic Network (UKANET) and Polar Earth Observing Seismic Network (POLENET). Interstation Rayleigh and Love wave phase velocity dispersion measurements at periods of 8-25 seconds were extracted from seismic ambient noise cross-correlograms by automated frequency-time analysis (AFTAN). The ensemble of interstation Rayleigh wave dispersion measurements was used to develop 2D Rayleigh wave phase velocity maps of West Antarctica at periods of 8-25 seconds by Fast Marching Surface Tomography (FMST) on a grid with a node spacing of 0.75deg. 'Local' 1D Rayleigh wave phase velocity dispersion curves were extracted by sampling the 2D Rayleigh wave phase velocity maps at grid node locations. The local 1D Rayleigh wave phase velocity dispersion curves were inverted for 1D shear wave (Vsv) structure to 40 km depth, and the ensemble of 1D shear wave (Vsv) profiles were subsequently gridded to produce the 3D shear wave (Vsv) model of West Antarctica from 10-40 km depth. Funding was provided by the NERC standard grant NE/L006065/1. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
 
Title 3D shear wave (Vsv) velocity model of West Antarctic uppermost mantle structure to 200 km depth 
Description 3D vertically-polarised shear wave (Vsv) velocity model of West Antarctic uppermost mantle structure to 200 km depth developed using data from the 2016-2018 UK Antarctic Seismic Network (UKANET) and Polar Earth Observing Seismic Network (POLENET). The model was constructed from the combination of fundamental mode Rayleigh wave phase velocity maps developed by ambient noise (periods 8-25 seconds) and earthquake data two-plane wave analysis (periods 20-143 seconds). Composite 'local' 1D Rayleigh wave phase velocity dispersion curves (periods 8-143 s) were extracted by sampling the 2D Rayleigh wave phase velocity maps at grid node locations spanning West Antarctica spaced at 100 km. The local 1D Rayleigh wave phase velocity dispersion curves were inverted for 1D shear wave (Vsv) structure to 200 km depth, and the ensemble of 1D shear wave (Vsv) profiles were subsequently gridded to produce the 3D shear wave (Vsv) model of West Antarctica uppermost mantle structure to 200 km depth. Funding was provided by the NERC standard grant NE/L006065/1. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
 
Title Annual melt onset, duration and end dates for the Antarctic Peninsula derived from Quikscat and ASCAT scatterometer Enhanced Resolution data, 1999-2017 
Description Surface melt onset, duration and end date for the Antarctic Peninsula from 1999/2000 to 2016/2017 at a spatial resolution of 2 km, derived from scatterometer data. Years 1999/2000 to 2008/09 are based on QSCAT data and 2009/10 to 2016/17 on ASCAT data. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Campaign GNSS results on rocky outcrops west of former Larsen B ice shelf, 2014-2015 
Description During the 2014/2015 season six temporary GNSS stations were deployed on rocky outcrops west of the former Larsen B ice shelf by the University of Leeds and BAS, in the region of the Flask and Leppard Glaciers. This was carried out as part of the NERC funded UKANET project. This is an area we have targeted with a space-based technique called radar interferometry (InSAR), which can provide dense measurements of uplift rates, and the temporary GNSS network were deployed to better understand the contribution of atmospheric noise to the InSAR results. Four were taken out in the same season, while the other two were pulled in the 2015/2016 season. Funding was provided by NERC grant NE/L006065/1. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/01379
 
Title Dataset from iWS 18 in Cabinet Inlet, Larsen C Ice Shelf, Antarctica, 2014-2017 
Description The data consists of 30 minute observations recorded by an automatic weather station (iWS 18) in Cabinet Inlet on Larsen C Ice Shelf on the Antarctic Peninsula. The iWS consists of a custom-built weather station unit, assembled at the Institute of Marine and Atmospheric research Utrecht (IMAU). There are sensors for air temperature, surface air pressure, relative humidity, as well as a gps, an acoustic snow height sensor, an ARGOS communication antenna, and three Lithium batteries that fuel the unit when solar radiation is absent. The unit is complemented by a propeller-vane Young anemometer measuring wind direction and speed. Additionally, all radiation fluxes are measured with a Kipp and Zonen CNR4 radiometer. This dataset runs from November 2014 to January 2017. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title UKANET data set form analysis of seismic ambient noise 
Description From analysis of seismic ambient noise: Rayleigh & Love wave phase velocities at periods from 8-30 seconds for POLENET stations (2008-2018) Rayleigh & Love wave phase velocities at periods from 8-30 seconds for UKANET stations (2016-2018) 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact Awaits the analysis of a second year's of data 
 
Title UKANET data set from analysis of earthquakes 
Description Rayleigh wave phase velocities at periods from 20-182 seconds for POLENET stations (2008-2018) Rayleigh wave phase velocities at periods from 20-182 s for UKANET stations (2016-2018) 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact Awaiting update from second year of data 
 
Title UKANET first season (Jan 2016 - Jan 2017) seismological data set 
Description Seismological data are sampled at 100 sps from 3 component 120s period Guralp 3T sensors. Data from 10 sensors were collected and uploaded on to the NERC GEF Seis-UK facility in Leicester. They are presently been quality controlled and will eventually be uploaded to an IRIS DMC in USA for sharing with collaborators 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact New area of broadband seismological coverage of West Antarctica 
 
Title UKANET second season seismological data set Jan 2017 - Feb 2018 
Description UKANET digital seismological recordings from 10 stations in Antarctica Jan 2017 - Feb 2018 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact Too early to tell 
 
Description UKANET - US Polenet partnership 
Organisation Colorado State University
Department Department Geosciences
Country United States 
Sector Academic/University 
PI Contribution This is a data-exchange collaboration whereby Polenet make available their seismological data in West Antarctica in exchange for the UK data seismological data when it arrives. We also have a research agreement in place to state our research intentions over the next 3 years. This is geographically based and directly related to the science proposed by the PI's to NERC
Collaborator Contribution This is a data-exchange collaboration whereby Polenet make available their seismological data in West Antarctica in exchange for the UK data seismological data when it arrives. We also have a research agreement in place to state our research intentions over the next 3 years. This is geographically based and directly related to the science proposed by the PI's to NERC
Impact Data exchange. We are already working on Polenet seismological data
Start Year 2015
 
Description UKANET - US Polenet partnership 
Organisation Penn State University
Department Department of Geosciences
Country United States 
Sector Academic/University 
PI Contribution This is a data-exchange collaboration whereby Polenet make available their seismological data in West Antarctica in exchange for the UK data seismological data when it arrives. We also have a research agreement in place to state our research intentions over the next 3 years. This is geographically based and directly related to the science proposed by the PI's to NERC
Collaborator Contribution This is a data-exchange collaboration whereby Polenet make available their seismological data in West Antarctica in exchange for the UK data seismological data when it arrives. We also have a research agreement in place to state our research intentions over the next 3 years. This is geographically based and directly related to the science proposed by the PI's to NERC
Impact Data exchange. We are already working on Polenet seismological data
Start Year 2015
 
Description UKANET - US Polenet partnership 
Organisation Washington University in St Louis
Department Department of Earth and Planetary Sciences
Country United States 
Sector Academic/University 
PI Contribution This is a data-exchange collaboration whereby Polenet make available their seismological data in West Antarctica in exchange for the UK data seismological data when it arrives. We also have a research agreement in place to state our research intentions over the next 3 years. This is geographically based and directly related to the science proposed by the PI's to NERC
Collaborator Contribution This is a data-exchange collaboration whereby Polenet make available their seismological data in West Antarctica in exchange for the UK data seismological data when it arrives. We also have a research agreement in place to state our research intentions over the next 3 years. This is geographically based and directly related to the science proposed by the PI's to NERC
Impact Data exchange. We are already working on Polenet seismological data
Start Year 2015
 
Description AGU 2017 Nield 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Nield, G., Whitehouse, P. L., Blank, B., van der Wal, W., O'Donnell, J. P., Stuart, G. W., Lloyd, A. J. and Wiens, D., 2017, The Sensitivity of Glacial Isostatic Adjustment in West Antarctica to Lateral Variations in Earth Structure, AGU, New Orleans, AGU General Assembly.
Year(s) Of Engagement Activity 2017,2018
 
Description AGU 2017 O'Donnell 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact O'Donnell, J. P., Dunham, C., Stuart, G. W., Brisbourne, A., Nield, G. A., Whitehouse, P. L., Hooper, A. J., Nyblade, A., Wiens, D., Aster, R. C., Anandakrishnan, S., Huerta, A. D., Wilson, T. J. and Winberry, J. P., 2017, Geothermal Heat Flux and Upper Mantle Viscosity across West Antarctica: Insights from the UKANET and POLENET Seismic Networks, AGU, New Orleans, AGU General Assembly.
Year(s) Of Engagement Activity 2017,2018
 
Description AGU 2018 Charlie Dunham 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Charlie Dunham, the PhD student studying the seismological recordings collected by the research project gave a poster presentation at the Fall meeting of AGU 2018
Year(s) Of Engagement Activity 2018
 
Description EGU 2018 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Nield, G., Whitehouse, P., van der Wal, W., Blank, B., Lloyd, A., Wiens, D., O'Donnell, J. P., Stuart, G. W. and Brisbourne, A., 2018, The influence of high resolution 3D Earth structure in West Antarctica on Glacial Isostatic Adjustment, EGU, Vienna, EGU General Assembly.
Year(s) Of Engagement Activity 2018
 
Description EGU 2018 Nield b 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Nield, G., Whitehouse, P., van der Wal, W., Blank, B., O'Donnell, J. P. and Stuart, G. W., 2018, The impact of lateral variations in lithospheric thickness on glacial isostatic adjustment in West Antarctica, EGU, Vienna, EGU General Assembly.
Year(s) Of Engagement Activity 2018
 
Description O'Donnell Macquarie 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact O'Donnell, J. P., 9th June 2017, Why understanding upper mantle viscosity is key to measuring West Antarctic Ice Sheet change, Department of Earth & Planetary Sciences Seminar, Macquarie University, Australia.
Year(s) Of Engagement Activity 2017
 
Description Poster presentation at WAIS (West Antarctica Ice Sheet) workshop in Washington DC, October 2nd - October 7th 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Attendance and poster presentation at the WAIS meeting, Washington DC, USA. This is an important workshop for all international scientists involved with West Antarctica earth science. The intended purpose of the poster was to present the international community the fact that we were recording seismological and GPS data in West Antarctica, meeting with Polenet collaborators and developing networks for future collaboration
Year(s) Of Engagement Activity 2016
 
Description Science talk at Rothera field station (Antarctica) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Whilst carrying out fieldwork in Antarctica to retrieve equipment I gave a science talk on the grant's aims and outcomes at Rothera, the working base of the British Antarctic Survey (BAS). The audience consisted a wide mix of people from fellow scientists to cooks on the base. There was an over full room, which contained some VIP's - government officials who had come down to Antarctica with the Director of BAS Jane Francis and 2 Financial Times journalists.
Year(s) Of Engagement Activity 2018
 
Description Talk by PhD student Charlie Dunham about his expedition with the British Antarctic Survey at Ilkley, Footloose travel agency 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact The talk was about Phd student Charlie Dunham's (University of Leeds, research assistant) experiences in West Antarctica, whilst servicing and maintaining the 10 NERC seismometers. He gave the talk and slide show to the general public interested in travelling to Antarctica on holiday.
Year(s) Of Engagement Activity 2017